In this video, I am going to describe how the computer system performs read and write operations?
A memory unit is one which stores binary information in group of bits called words. Data input lines are one which provide the information to be stored into the memory.
Data output lines are one which carry the information out from the memory.
The control lines Read and write specifies the direction of transfer of data. Basically, in the memory organization, there are 2l memory locations indexing from 0 to 2l-1 where l (small letter L) is the address buses.
We can describe the memory in terms of the bytes using the following formula:
Where, l specifies the total address busses and N specifies the memory in bytes.
Let us take an example to make it clear:
1kb=2 10 bytes 32kb=25 X 210 bytes=215 bytes
Memory operation takes help of two registers precisely to access the main memory, they are:
Memory Address Register (MAR):
This register is used to store the address of the memory location where the operation is actually being performed.
Memory Data Register (MDR):
This register is used to store the data on which the actual operation is being performed.
Let us discuss briefly how read and write operation actually takes place:
Memory Read Operation:
Memory read operation transfers the word to the address lines and activates the read control line.
In the above diagram MDR holds a garbage value and MAR contains 1010 memory addresses.
After the execution of read instruction, the data of memory location 1010 will be read and the MDR will get restructured with the value of the 1010 memory location as shown below.
Memory Write Operation:
Memory write operation transfers the address of the word to the address lines and the data bits get transferred which are stored in memory of the data input lines. Then activates the write control line.
In the above diagram the MAR contains 1010 and MDR contains WIP. After the execution of write instruction WIP gets written at 1010 memory location as shown below:
This is how memory read and write operation takes place where the MAR and MDR registers plays a vital role in conducting the operation.
Hence, we end the discussion here and hope have cleared all your doubts related to the topic.
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